Femtosecond high-power Ti:sapphire chirped-pulse amplification (CPA) laser technology at 800 nm of wavelength has been widely and almost exclusively used over last two decades for studying ultrafast nonlinear optics and strong-field phenomena. Recently ultrafast optical parametric chirped-pulse amplification (OPCPA) technology has made a rapid progress, so that various wavelengths are available at high intensities. The wavelength selectivity provides interesting opportunities in ultrafast nonlinear optics and strong-field phenomena driven especially at mid-infrared (MIR) wavelengths. High-harmonic generation (HHG) driven by MIR wavelengths has been proven to be a reliable way to achieve a tabletop coherent water-window soft X-ray (280-540 eV) or keV source. On the other hand, the super-continuum generation (SCG) in the MIR range is highly useful for detecting biomedical materials and air pollutants with the resonant fingerprints of the common molecules, such as H2O, CO2, CO, and NH4. The highly nonlinear laser filamentation process enables the SCG in bulk dielectrics and gases.

In this presentation, I review our recent progress on a multi-mJ MIR (2.1 m) OPCPA system operating at a kHz repetition rate, pumped by a picosecond cryogenically cooled Yb:YAG laser. Using this novel MIR source, we demonstrate high-flux soft X-ray HHG up to the water-window range. In addition, I present the MIR filamentation in dielectrics showing 3-octave-spanning SCG and sub-2-cycle self-compression. I will also discuss novel high-energy pulse synthesizer technology based on multi-color OPCPA systems. The work presented here provides an excellent platform of next-generation strong-field laser technology.